But police believe the amateur photographer is alive because her phone was used for a Skype call on Wednesday and turned on again Thursday, the Sabah newspaper reported, according to the Turkish daily Hurriyet.

Cops briefly detained a man who exchanged online messages with Sierra after meeting her online four months ago, contacted her while she was in Istanbul and made plans to rendezvous with her on a bridge she wanted to photograph, Hurriyet said.

The man reportedly told police the two never connected, and investigators are now hoping to question three other people she corresponded with on Facebook and Twitter.

Sierra left for her first trip abroad on Jan. 7 — flying solo after a close friend dropped out of the prepaid trip, her family has said.

Her husband, Steven Sierra, said his wife stayed in close contact, talking to him and their children, ages 9 and 11, by phone and Skype.

The last communication from her came Jan. 21, when she sent her sister a brief message saying she would be home the next day.

When she didn't show up at the airport, her husband called her hostel, which said her passport and other personal items were still there.

Police uncovered surveillance-camera footage of Sierra walking around Istanbul during her visit; she appeared to be alone and well.

Steven Sierra and Sarai's brother, David Jimenez, flew to Turkey earlier this week and turned over her online communications to police.

"I don't want to come home without my sister," Jimenez told NBC New York before the trip.